GNS Science, along with the National Institute for Water and Atmospheric Research (Niwa), have just wrapped up a major project to revise the New Zealand National Seismic Hazard Model (NSHM).

A number of newly identified faults have now been added to the model, raising the total number of known fault lines by about 200 - to nearly 530.

Niwa said a particularly large fault found offshore near Canterbury had the potential to cause a significant tsunami.

The large fault was found in the bedrock under Pegasus Bay shortly after the February Christchurch quake when GNS Science and Niwa conducted a survey of 800 square kilometres.

Scientist Philip Barnes said New Zealand had to prepare for marine quakes in many locations.

"There are many earthquake faults on the sea-floor around our coasts, and the next major earthquake could be centred offshore. So it highlights the need for coastal marine investigations of active earthquake faulting, for both ground-shaking hazards and tsunamis," he said.